A bidding decision index for construction contractors

Results from applying the model on a sample of contractors, the majority of whom were international and operating in Egypt, reinforces the credibility of the developed methodology, claim the authors.     

Congestion prevention in broadband wireless access systems: An economic approach

While the demand for mobile broadband wireless services continues to increase, radio resources remain scarce. Even with the substantial increase in the supported bandwidth in the next generation broadband wireless access systems (BWASs), it is expected that these systems will severely suffer from congestion, due to the rapid increase in demand of bandwidth-intensive multimedia services. Without efficient bandwidth management and congestion control schemes, network operators may not be able to meet the increasing demand of users for multimedia services, and hence they may suffer an immense revenue loss. In this paper, we propose an admission-level bandwidth management scheme consisting of call admission control (CAC) and dynamic pricing. The main aim of our proposed scheme is to provide monetary incentives to users to use the wireless resources efficiently and rationally, hence, allowing efficient bandwidth management at the admission level. By dynamically determining the prices of units of bandwidth, the proposed scheme can guarantee that the number of connection requests to the system are less than or equal to certain optimal values computed dynamically, hence, ensuring a congestion-free system. The proposed scheme is general and can accommodate different objective functions for the admission control as well as different pricing functions. Comprehensive simulation results with accurate and inaccurate demand modeling are provided to show the effectiveness and strengths of our proposed approach.     

Network coding for wireless communication networks

This special issue includes a collection of 19 outstanding research papers which cover a diversity of topics on the application of network coding in wireless communication networks.     

Performance analysis of differentiated QoS in IEEE 802.11e WLANs

This paper proposes a multi‐dimensional Markov model to analyse the performance of the IEEE 802.11e EDCF MAC protocol. Based on this model, we present extensive performance evaluation in terms of throughput, throughput ratios, and access delay of flows of distinct priorities under RTS/CTS mode. We also provide quantitative analysis of the impact of prioritized parameters, i.e. Arbitration InterFrame Space (AIFS), Contention Window (CW) on Quality of Service (QoS) differentiation. The accuracy of the proposed model is verified by means of comparing the numerical results obtained from both analytical model and simulations. Our research can be used as a guideline for the prediction of how flows belonging to a certain Traffic Category (TC) perform with their TC‐specific parameters, as well as designing EDCF‐based WLANs and tuning the parameters to achieve the desirable differentiated QoS objectives. Copyright © 2005 John Wiley & Sons, Ltd.     

Inverse Problem of the Interval Linear System of Equations

Given a nonsingular central matrix , a central vector and a prescribed interval solution vector , it is required to find the maximum allowable deviation or so that the solution of the interval linear system is contained in . Special cases for and are considered and bounds on the entries of and are obtained either in a closed form, whenever possible, or via solving a specially designed constrained optimization problem. Received: August 25, 1997; revised February 20, 1999     

Waterpipe smoking: construction and validation of the Lebanon Waterpipe Dependence Scale (LWDS-11).

Waterpipe smoking is becoming fashionable in Lebanon, but no studies have studied nicotine dependence related to waterpipe smoking. A score was constructed from 21 items and subsequently submitted to two factor analyses, which led to the extraction of four factors. Reliability and test-retest reproducibility were measured. Convergent construct validity and discriminant validity also were assessed for different smokers' samples. The Lebanon Waterpipe Dependence Scale-11 (LWDS-11) was composed of four subscales, the first representing nicotine dependence, the second negative reinforcement, the third psychological craving, and the fourth positive reinforcement. Internal consistency and test-retest reproducibility were adequate, and the subscales correlated adequately with measurements of nicotine metabolites, exhaled carbon monoxide levels, and the frequency of waterpipe smoking. The LWDS-11 discriminated between mild, moderate, and heavy waterpipe smokers, based on a threshold score of 10. Results were biologically and psychologically sound. This is the first scale to characterize waterpipe dependence. With further improvement and confirmation, it could become a useful clinical and epidemiological tool.     

Aureobasidium pneumonia in a post liver transplant recipient: a case report

This is the first report of Aureobasidium (A.) pullulans as an opportunistic pulmonary infection in a liver transplant recipient. A 46-year-old caucasian man had an orthotopic liver transplant in 1988. His liver disease was primary sclerosing cholangitis. He required 2 subsequent liver re-transplants for primary graft non-function and acute rejection. The patient had been living in the California desert for two months prior to admission and presented with ventilator-dependent acute respiratory failure and hemodialysis-dependent acute renal failure. Imaging studies revealed severe bilateral infiltrates. His initial bronchoalveolar lavage (BAL) and brushings grew A. pullulans. Pancultures, including sputum and throat cultures, were negative for bacterial or other fungal organisms. The patient responded to pulmonary support and aggressive systemic antifungal agents while being maintained on cyclosporine and prednisone for immunosuppression. He was discharged to a skilled nursing facility 37 days after hospitalisation. Delay in discharge was primarily due to severe malnutrition and renal impairment. Opportunistic fungal infections continue to be a major problem in immunosuppressed patients including liver transplant recipients. Here we report a pulmonary infection with Coccidioides (C.) immitis and superinfection with A. pullulans. Opportunistic infections such as A. pullulans can be treated successfully with systemic fluconazole when amphotericin B is not well tolerated.     

Asphalt Works Subcontracting Disputes in Large Construction Programs

Subcontracting is a common, and sometimes warranted, practice on large construction projects. However, it is also well recognized that disputes are likely to develop between subcontractors and general contractors in trying to achieve target objectives of cost, quality, and time. This paper tackles quality- and time-related disputes that are peculiar to the case of subcontracting asphalt works under a large construction program, such as that of a new airport construction. In particular, it reports on disagreements regarding the achieved thickness and surface smoothness of the constructed asphalt concrete layer, and on activity-interfacing and delay-attribution issues resulting from improper contractual and scheduling practices. Factors believed to be relevant to both classes of disputes are identified, and analyses are offered to pinpoint significant anomalies. Finally, arguments are developed and recommendations given, that reflect best industry practices whose application could help minimize the likelihood of facing such disputes in the future.     

Characterizing multi‐hop localization for Internet of things

Deployments over large geographical areas in the Internet of Things (IoT) pose a major challenge for single‐hop localization techniques, giving rise to applications of multi‐hop localizations. And while many proposals have been made on implementations for multi‐hop localization, a close understanding of its characteristics is yet to be established. Such an understanding is necessary, and is inevitable in extending the reliability of location based services in IoT. In this paper, we study the characteristics of multi‐hop localization and propose a new solution to enhance the performance of multi‐hop localization techniques. We first examine popular assumptions made in simulating multi‐hop localization techniques, and offer rectifications facilitating more realistic simulation models. We identify the introduced errors to follow the Gaussian distribution, and the estimated distance follows the Rayleigh distribution. We next use our simulation model to characterize the effect of the number of hops on localization in both dense and sparse deployments. We find that, contrary to common belief, it is better to use long hops in sparse deployments, while short hops are better in dense deployments – despite the traffic overhead. Finally, we propose a new solution that decreases and manages the overhead generated during the localization process. Copyright © 2016 John Wiley & Sons, Ltd.     

Vacuum Technology Considerations For Mass Metrology

Vacuum weighing of mass artifacts eliminates the necessity of air buoyancy correction and its contribution to the measurement uncertainty. Vacuum weighing is also an important process in the experiments currently underway for the redefinition of the SI mass unit, the kilogram. Creating the optimum vacuum environment for mass metrology requires careful design and selection of construction materials, plumbing components, pumping, and pressure gauging technologies. We review the vacuum technology¹ required for mass metrology and suggest procedures and hardware for successful and reproducible operation.